Composite pigment original, composite pigment, process for producing ink composition, and ink composition

Abstract

The present invention provides a composite pigment original having a structure comprising a resin layer and a pigment layer sequentially stacked on a sheet-shaped substrate surface, the pigment layer having a structure that at least a silicon oxide layer, a metal or metal compound layer and a silicon oxide layer are sequentially stacked. Furthermore, a composite pigment obtained from the composite pigment original, a process for producing an ink composition using the composite pigment original, and an ink composition obtained by the production process are disclosed.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a composite pigment original and a composite pigment. More specifically, the present invention relates to a composite pigment original and a composite pigment, which are used for an ink-jet recording ink and excellent in the storage stability and dispersibility.[0002]The present invention further relates to a process for producing an ink composition using the composite pigment original, and an ink composition obtained by the production process. More specifically, the present invention relates to a process capable of efficiently producing an ink composition for use in an inkjet recording ink, which has a metallic luster and is excellent in the storage stability and dispersibility, and an ink composition produced by the process.BACKGROUND OF THE INVENTION[0003]The inkjet recording method is a method of ejecting an ink droplet from a fine nozzle head and recording a letter or a figure on the surface of a recording medium such...

AI Technical Summary

Benefits of technology

[0020]The present inventors have found that the metal powder used in a metallic pigment is highly reactive and has a problem in the storability and reactivity with water but when constituted as a composite pigment having a stacked structure of silicon oxide layer / metal or metal compound layer / silicon oxide layer, chemical stability is attained, reaction with water is prevented, the long-term storability is remarkably enhanced and furthermore, excellent quality as an aqueous inkjet ink composition is obtained; when constituted as a composite pigment having a stacked structure of silicon oxide layer / coloring material layer / metal or metal compound layer / coloring material layer / silicon oxide layer, arbitrary coloration is also facilitated; and when a stacked part of a resin layer and a sheet-shaped substrate is employed for the above-described stacked structure, the stacked structure body is easily separated and pulverized in an aqueous liquid. The present invention has been accomplished based on these findings.

[0021]That is, the present invention relates to the following composite pigment original and composite pigment.

[0022](1) A composite pigment original having a structure comprising a resin layer and a pigment layer sequentially stacked on a sheet-shaped substrate surface, the pigment layer having a structure that at least a silicon oxide layer, a metal or metal compound layer and a silicon oxide layer are sequentially stacked.

[0023](2) The composite pigment original as described in (1) above, wherein the thickness of the pigment layer is from 100 to 500 nm.

[0024](3) The composite pigment original as described in (1) above, wherein the resin layer comprises a polyvinyl alcohol, a polyethylene glycol, a polyacrylic acid, a polyacrylamide or a cellulose derivative.

[0025](4) The composite pigment original as described in (1) above, wherein the silicon oxide layer is formed of a silicon alkoxide or a polymer thereof by a sol-gel method.

Problems solved by technology

However, the dispersant merely adsorbed to the pigment surface sometimes deteriorates the dispersed state by repeating desorption and adsorption.

However, metal powder and the like easily available on the market are low in the luster due to surface non-uniformity originated in the production process or because of their high reactivity, restricted in view of use, for example, the metal powder and the like must be stored in an inert gas atmosphere away from contact with water or the like.

Furthermore, the reactivity with moisture in air is also high and this gives rise to a problem in the storability, for example, the quality deteriorates during a long-term storage due to generation of hydrogen or gelling.

In addition, the metal powder is not easily blended with a coloring material for imparting an arbitrary color tone, and desired coloration is difficult to attain.

The highly active metal powder such as aluminum readily reacts with water in an aqueous solvent and can be hardly applied to an ink using an aqueous solvent, because problems arise during storage, such as generation of hydrogen or gelling.

Furthermore, in the case of storing a conventional metallic pigment or an ink, coating material or the like containing the metallic pigment, these cannot be stored for a long time because of problems of reactivity with water and surface oxidation.

In addition, the metal powder for use in conventional metallic pigments usually has a particle size as large as 20 to 30 μm and cannot be used as it is for the inkjet ink.

Not only the particle size but also the specific gravity is large and therefore, the metal powder is bad in the dispersion stability and readily precipitates.

The dispersion stability cannot be satisfactorily improved even by using the above-described microencapsulation technique.

However, the technique of Patent Document 2 cannot overcome the problem regarding reactivity with water.

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